Transgenic and knockout mice have played a very important role in biomedical research for the development of animal models for human diseases and for addressing many different biological questions. The transgenic mouse core facility of the NYU School of Medicine combines the services and resources of the Skirball Institute and the Cancer Institute. The TgESCF currently provides four basic services: production of transgenic mice by zygote injection, production of ES cell chimeras by blastocyst injection or morula aggregation, rederivation of mouse strains, and sperm cryopreservation. Over the next 5 years, the transgenic facility will continue to provide these services, but will also provide new services such as the generation and genotyping of knockout ES cell lines, embryo cyropreservation, the purification of DMA constructs, and assisted reproduction techniques. In the past year, transgenic mice have been produced using inbred FVB/N and C57BL/6 mice, and ES cell chimeras have been produced by injection of ES cells into C57BL/6 blastocysts. To enable investigators to house pathogen-free animals in the Skirball animal facility, rederivation of mouse strains has continued to be important, especially as new staff are recruited who work with mice. Over the past 10 years the .transgenic facility has generated -3,600 transgenic founders from ~670 DMA constructs (including BAC-based constructs), generated ES cell chimeras from -370 ES cell knockout lines and rederived -460 mutant lines. During the period of the current Cancer Center Support Grant (2002-2006), 251 DNA constructs were injected and 877 founders were obtained, chimeras were made from 143 targeted ES cell clones, and 261 mouse strains were rederived. We also froze sperm from 17 mutant mouse strains. In addition to these services, the core director and coordinator provided researchers with support related to work with transgenic and knockout mice, such as training in mouse husbandry and consultation in transgenic and ES cell approaches.